There are many applications which rely on a comparison of biometric data. Examples of such applications include biometric authentication or identification of a person. In this type of application, biometric data are captured for different persons during an enrollment phase and stored in a database. Next, in a later step, in order to identify or authenticate someone, biometric data is captured for this person. On the basis of a comparison between the biometric data stored in the database and the acquired biometric data, the decision can then be made as to whether the person is authenticated or identified. Below, an acquired biometric data item is also referred to as “an acquired biometric data item”.
Thus the biometric authentication or identification is based on a comparator which compares biometric data items. After the comparison, this comparator provides an indication of the similarity between two biometric data items, generally referred to as the “score”. This indication allows determining a level of resemblance between the two compared biometric data items, and thus allows deciding whether these two biometric data items come from the same individual.
In certain applications based on a biometric data comparator, it is important to be able to compare biometric data easily, using simple operations. However, it is not always easy to obtain such simplicity of operation when manipulating biometric data.
It is known to create biometric data indexing in a biometric database. The biometric data are assembled into groups of prints having the same index or a similar index (if considering the Hamming distance for example). When wanting to check whether a captured print corresponds to a legitimate print in the database, the index for the captured print can be calculated, and the captured print compared only with the prints in the database having an identical or similar index, which reduces the number of comparisons and therefore accelerates the search (the known comparison algorithms are generally slow). The index alone does not allow avoiding later comparison steps with all the biometric data for the group concerned.